I own a 1998 E300 Turbodiesel sedan, 1999 E320 4Matic wagon, and 2001 E320 sedan...the 1998 sedan and 1999 wagon have four airbags (dual front airbags and front side airbags). I am aware that 1999 sedans (not wagons) have six airbags (dual front airbags, front side airbags, and side curtain airbags). The 2000+ sedans and wagons have eight airbags (dual front airbags, front and rear side airbags, and side curtain airbags). This information is true for all North American models.

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1982 300D-T (sold)
1988 300E (sold)
1994 E320 Wagon (sold)
1995 E320
1998 E300D-T
1999 E3204M Wagon
2001 E320
2005 E320 CDI